A buffer is for example incorporated into an I/O cell of an integrated circuit. Conventionally, there are two broad families of buffers.
A first family includes what are called “open-drain” buffers comprising only a single type of MOS transistor. Thus a buffer of this type, for example an output buffer, comprises a MOS transistor, for example an nMOS transistor, the gate of which is intended to receive a signal from another component, the drain of which forms a signal output of the buffer and is connected to the I/O pin of the cell and the source and substrate of which are connected to another pin of the cell intended to be grounded.
The cell moreover comprises protection means (for example diodes or else nMOS transistors the gate of which is directly grounded (gate-grounded nMOS) and the substrate of which is also directly grounded) intended to protect, against electrostatic discharges that may occur across the I/O pin and said other pin, a component connected to these two pins.
A second family includes buffers comprising CMOS transistors (nMOS and pMOS) connected in series via a common node and having their gates connected. The gates then receive for example a signal from another component, and the common connection node, in series, forms a signal output. Here again the cell containing the buffer also includes conventional means for protecting against electrostatic discharges.